A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus are conventionally used, for example, in the manufacture of integrated circuits (ICs), flat panel displays and other devices involving fine structures.
It is desirable to reduce the size of features in a lithographic pattern because this allows for a greater density of features on a given substrate area. In photolithography, the increased resolution can be achieved by using light of shorter wavelength. However, there are problems associated with such reductions. Current systems are starting to adopt optical sources with wavelengths in the 193 nm regime, but even at this level, diffraction limitations become a barrier. At lower wavelengths, the transparency of materials is very poor. Optical lithography machines capable of enhanced resolutions require complex optics and rare materials and are consequently very expensive.
An alternative for printing sub-100 nm features, known as imprint lithography, comprises transferring a pattern to a substrate by imprinting a pattern into an imprintable medium using a physical mold or template. The imprintable medium can be the substrate or a material coated on to a surface of the substrate. The imprintable medium can be functional or can be used as a “mask” to transfer a pattern to an underlying surface. The imprintable medium can, for example, be provided as a resist deposited on a substrate, such as a semiconductor material, to which the pattern defined by the template is to be transferred. Imprint lithography is thus essentially a molding process on a micrometer or nanometer scale in which the topography of a template defines the patterns created on a substrate. Patterns can be layered as with optical lithography processes so that in principle imprint lithography could be used for such applications as IC manufacture.
The resolution of imprint lithography is limited only by the resolution of the template fabrication process, for example, imprint lithography has been used to produce features in the sub-50 nm range with significantly improved resolution and line edge roughness compared to that achievable with conventional optical lithography processes. In addition, imprint processes do not require expensive optics, advanced illumination sources, or specialized resist materials typically required by optical lithography processes.
Current imprint lithography processes can have a number of drawbacks particularly with regard to achieving overlay accuracy and high throughput. However, significant improvements in resolution and line edge roughness attainable are from imprint lithography.
A problem which can arise during imprint lithography is that gas bubbles, also known as air inclusions, can be trapped underneath an imprint template during the imprint process. These trapped gas bubbles do not migrate out from beneath the imprint template, but instead stay there for the duration of the imprint process. When the imprint template is removed from the imprintable material (which can be a UV curable resin), an area of the imprinted pattern will be incomplete or otherwise damaged at the location of the gas bubble.
With the traditional used UV curable and thermally deformable resins, separating the stamp from the resin, after imprinting, can be particularly problematic. That is, it is difficult to separate the resin and the stamp in a way that is not impeded by the stamp sticking to the resin, particularly when a vacuum has been used to aid the impress process. Additionally, newer applications for Imprint Stamping require patterning on two sides of the substrate, further complicating the problems noted above.
What is needed, therefore, is a system and method to alleviate the challenge of separating a stamp from the resin after an imprint stamp is used to imprint a pattern into the resin. What is also needed is a system and method enhance the speed of imprint stamping on two sides of the substrate.